Outside air water source heat pump

ABSTRACT

A thermal system and method are provided configured for improved efficiency. The system is typically configured to provide outside air to a building with the combination of a ground/water source heat pump and a dedicated outside air unit.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from Provisional Application Ser. No. 61/588,407 filed Jan. 19, 2012; the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention is related generally to thermal systems and to those typically used in providing outside air to a building. More particularly, the present invention is related to a thermal system which typically utilizes a ground/water source heat pump and a dedicated outside air unit pump providing outside air to a building.

2. Background Information

Over the last decade or so, there has been a trend of providing outside air to buildings using dedicated outside-air units. Dedicated outside-air units result in better control of building pressurization, a more consistent introduction of required outside-air quantities, and better management of water vapor removal (often called “latent cooling”) from the outside air, which is especially important at part-load operating conditions, which occur during 97-plus percent of all operating hours. Some designers extend this concept and decouple both the outside-air load and the space latent load from space air-conditioning systems. In dedicated outside-air units, this is achieved by lowering the supply-air dew-point temperature far enough below the desired space dew-point temperature to offset space latent gains. This eliminates or minimizes condensed moisture at most if not all space air-conditioning units. Eliminating or minimizing condensed moisture at a space-conditioning unit's cooling coils provides indoor-air-quality benefits, reduces maintenance costs, and may eliminate the requirement for double-wall casings in the unit. However, conditioning outside air delivered to a building to the comfortable levels of humidity and temperatures consumes more energy compared to recycled air.

A heat pump transfers heat from a heat source (e.g., well water or outside air) at one temperature to a heat sink at a lower temperature. The greater the difference in temperature between the heat source and the heat sink, the more work the heat pump must do and consequently the more it will cost. Heat pumps accommodate fluid types including but not limited to water, propylene glycol and ethylene glycol. The head pressure control strategy makes a wide range of operating temperatures acceptable.

As the source temperature declines so will the efficiency of the heat pump. Because ground water stays at a relatively constant temperature most of the year, a ground water-source heat pump will yield a much higher average annual coefficient of performance (COP) than does a heat pump which gathers heat from the surrounding air. A typical annual average COP for a water source heat pump would range from about 3.5 to 4.5 while that of an air-source heat pump might yield an average COP of 1.7 to 2.2.

There is a need in the art for greater efficiency in thermal systems using outside air. One preferred embodiment of the present invention combines the efficiency of a water source heat pump with the dedicated outside-air approach to provide a very economical system and method for dedicated outside-air units.

BRIEF SUMMARY OF THE INVENTION

In one aspect, a thermal system typically includes an airflow duct; a compressor; a first heat exchanger which is in the airflow duct and has a first heat exchanger inlet in fluid communication with the compressor and a first heat exchanger outlet; a second heat exchanger which is in the airflow duct and which has a second heat exchanger inlet and a second heat exchanger outlet; a compressor discharge line connected to and extending downstream from the compressor; a first heat exchanger discharge line connected to the first heat exchanger outlet; a mixture line which is connected to the second heat exchanger inlet and is in fluid communication with the compressor discharge line and first heat exchanger discharge line; and a refrigerant which is movable through the first heat exchanger, second heat exchanger, compressor, compressor discharge line, first heat exchanger discharge line, and mixture line.

In another aspect, a method typically includes providing first and second heat exchangers in an airflow duct; discharging heated refrigerant from a compressor; moving a first portion of the heated refrigerant discharged from the compressor into the first heat exchanger; releasing the first portion from the first heat exchanger; mixing a second portion of the heated refrigerant discharged from the compressor with the first portion released from the first heat exchanger to form a mixture; delivering the mixture to the second heat exchanger; and blowing air through the airflow duct to transfer heat from the first and second heat exchangers to the air.

In another aspect, a method typically includes providing first and second heat exchangers in an airflow duct; moving a first portion of heated gaseous refrigerant into the first heat exchanger so that the refrigerant is cooled and discharged from the first heat exchanger as heated liquid refrigerant; mixing a second portion of the heated gaseous refrigerant with the discharged heated liquid refrigerant to form a mixture; delivering the mixture to the second heat exchanger; and blowing air through the airflow duct to transfer heat from the first and second heat exchangers to the air.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

A preferred embodiment of the invention, illustrative of the best mode in which Applicant contemplates applying the principles, is set forth in the following description and is shown in the drawings and is particularly and distinctly pointed out and set forth in the appended claims.

FIG. 1 is a schematic view of an embodiment of the present thermal system.

Similar numbers refer to similar parts throughout the drawings.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present thermal system and method is shown generally at 1 in FIG. 1. System 1 is in the form of an outside air water source heat pump or ground source heat pump which is the combination of a ground or water source heat pump and a dedicated outside air unit used for providing outside air to an enclosed airspace 2 of a building 4. The outside air and the direction of the flow thereof during the operation of system 1 is represented at Arrow A, which also represents a blower for blowing the outside air in this direction. The heat pump of the present invention typically uses as a heat source underground water 6, such as ground water within the ground or soil, well water, or water in a pond, lagoon or lake, etc. at a depth which provides substantially constant temperature as the heat source throughout the year. Water 6 is thus from below surface 8 of soil, earth or ground 10 and may be, as represented by 11, within a well, pond, lagoon, lake, river and so forth.

The heat pump of system 1 includes a compressor 12, a condenser or refrigerant-to-air heat exchanger 14 which is within an airflow conduit or duct 15 of the dedicated outdoor air unit, and a post heater or second refrigerant-to-air heat exchanger 16 which is also within airflow duct 15 downstream of heat exchanger 14. Air duct 15 includes an upstream end defining an entrance opening 17 which opens to and is in fluid communication with the outside air, and a downstream end defining an exit opening 19 which opens to and is in fluid communication with airspace 2 of building 4. The heat pump further includes an expansion valve 18 and a heat exchanger external to air duct 15 and building 4 and typically an underground or ground-coupled heat exchanger 22 typically in the form of a direct exchange coil evaporator. Heat exchanger 22 typically uses what is known in the art as a vertical loop, a horizontal loop or a pond loop. Vertical loops are typically used in wells and extend downward below the surface typically 200 to 300 feet deep. The horizontal loop is typically placed within the ground or trench at a depth of about 4 to 10 feet below surface 8. A pond loop is typically a coil in a lagoon, pond or lake and positioned at deeper than 10 feet.

System 1 further includes an outside air temperature sensor 24, an inside air temperature sensor 26, and a flow rate control 28 typically including a flow rate control valve for controlling the flow rate of refrigerant as discussed further below. Control 28 is in electrical or other communication with temperature sensors 24 and 26 in order to receive signals from each of the sensors indicating the temperature at the location of the given sensor. Sensor 24 is located in the outside air broadly adjacent entrance opening 17 and upstream of heat exchanger 14, and is thus external to building 4 whereby sensor 24 senses the temperature of the outside air prior to its being heated within airflow duct 15. Temperature sensor 26 is within airspace 2 of building 4 in order to sense the inside air temperature within airspace 2.

The heat pump further includes a compressor discharge line or hot gas line 30 which is connected at an upstream end thereof to an outlet of compressor 12 and at a downstream end thereof to an inlet of first heat exchanger 14. More particularly, line 30 branches at an intersection into a first branch or line 30A which is connected at a downstream end thereof to the inlet of first heat exchanger 14, and a second branch or line 30B extending downstream from the intersection with line 30A to connect to a first heat exchanger discharge line or hot liquid line 32 at an mixing location such as intersection 34, which may also represent a mixing chamber. Line 32 is connected at an upstream end thereof to an outlet of first heat exchanger 14 and at a downstream end thereof to an inlet of second heat exchanger 16. Thus, line 32 extends downstream from the first heat exchanger outlet to the second heat exchanger inlet, and intersection 34 in the exemplary embodiment is along line 32 between the first heat exchanger outlet and the second heat exchanger inlet.

Inasmuch as FIG. 1 illustrates the use of system 1 in the heating mode, intersection 34 is thus downstream of the outlet of first heat exchanger 14 and upstream of the inlet of second heat exchanger 16. Line 32 becomes a hot liquid and hot gas mixture line 36 at intersection 34 which thus extends downstream therefrom to the connection with the inlet of second heat exchanger 16. The heat pump further includes a second heat exchanger discharge line or cooled liquid line 38 which is connected at an upstream end thereof to an outlet of second heat exchanger 16 and at a downstream end thereof to the inlet of expansion valve 18.

System 1 typically uses a single closed refrigerant recirculation loop such that an expansion valve discharge line or cooled liquid line 40 is connected at an upstream end thereof to an outlet of expansion valve 18 and at a downstream end thereof to an inlet of heat exchanger 22. A heated liquid line 42 is connected to an outlet of heat exchanger 22 and an inlet of compressor 12. The use of heat exchanger 22 in combination with lines 40 and 42 provides a direct exchange of heat from the soil, underground water within the soil, well, pond, lagoon or lake to the refrigerant passing through heat exchanger 22 via lines 40 and 42.

Each of lines 30 (including 30A and 30B), 32, 36, 38, 40 and 42 may also be thought of as segments of the refrigerant recirculation loop through which the refrigerant is delivered, moves, flows, travels or circulates from the outlet of compressor 12 and back to the compressor outlet through the other components of the recirculation loop, namely heat exchangers 14 and 16, flow rate control valve 28, expansion valve 18 and third heat exchanger 22. Thus, some of these segments may also be thought of as parts of a given line. For example, segments 38, 40 and 42 may be termed a second heat exchanger discharge or release line which is connected to and extends downstream from the outlet of second heat exchanger 16 to the compressor 12 inlet. Similarly, segments 38 and 40 may be termed a second heat exchanger discharge or release line which is connected to and extends downstream from the outlet of second heat exchanger 16 to the third heat exchanger 22 inlet.

Each of lines 30 (including 30A and 30B), 32, 36, 38, 40 and 42 are also understood to be in or provide fluid communication between the respective components to which they are connected. Each is also understood to extend downstream from a given component to which it is connected and upstream from another component to which it is connected. Thus, for example, line 30 is connected to and extends downstream from the outlet of compressor 12 via portion 30A to the first heat exchanger 14 inlet, and likewise extends upstream from the exchanger 14 inlet to the compressor 12 inlet, such that line 30 is in fluid communication with or provides fluid communication between compressor 12 and first heat exchanger 14. Similarly, line 30 is connected to and extends downstream from the outlet of compressor 12 via portion 30B to the mixing location or intersection 34, and likewise extends upstream from the mixing location or intersection 34 to the compressor 12 inlet, such that line 30 is in fluid communication with or provides fluid communication between compressor 12 and the mixing location or intersection 34. As would be understood by one skilled in the art, the other lines noted herein may also be described in a similar manner but are not in the interest of brevity. Applicant reserves the right to claim relationships such as these which would be understood to one skilled in the art especially in light of the figures.

In the heating mode, the heat pump generally transfers heat from heat exchanger 22 to heat exchangers 14 and 16 via the refrigerant moving through the single recirculation loop which includes lines 40 and 42 although additional recirculation loops may be used. The blower of the dedicated outside air unit thus blows outside air through the air passage of airflow duct 15 to be heated by heat exchangers 14 and 16 so that the heated air blows into airspace 2 of building 4. More particularly, compressor 12 compresses and discharges or releases the refrigerant so that the refrigerant in the form of a hot or heated gaseous refrigerant moves from the outlet of the compressor through line 30 and into heat exchanger 14 via the inlet thereof. More particularly, a portion of the heated gas moves into or enters first heat exchanger 14 via line 30A while a portion of the heated gas also moves through line 30B into line 32, 36 at intersection 34. Heat from the refrigerant is thus rejected at heat exchanger 14 to the outside air blowing through duct 15, thus increasing the temperature of the outside air from a first outdoor air temperature to an initially heated air temperature of the air downstream of heat exchanger 14 and upstream of heat exchanger 16. The extraction of heat from the refrigerant within heat exchanger 14 thus cools the refrigerant so that it changes state from a heated gaseous refrigerant into a hot or heated liquid refrigerant which is discharged or released from heat exchanger 14 through its outlet and moves downstream through line 32, where the heated liquid refrigerant mixes with the portion of the hot gaseous refrigerant passing through line 30B at mixing location or intersection 34, where this mixture continues to travel through mixture line 36 and is delivered into heat exchanger 16 via the inlet thereof.

Thus, a refrigerant mixture of the hot liquid and hot gas is created at intersection 34 whereby this combination of the refrigerant moves through line 36. (The term mixture here refers merely to the mixing of the hot liquid and hot gas of the same refrigerant and thus is not indicative of mixing two or more different refrigerants with one another.) This refrigerant mixture thus rejects heat via heat exchanger 16 to the outside air which has already been initially heated by the first heat exchanger 14, thus further increasing the temperature of the outside air as it continues downstream travel through duct 15. Thus, the second heat exchanger 16 further heats or raises the temperature of the outside air to a desired pre-entry temperature prior to entering airspace 2 of building 4, wherein the outside air mixes with inside or indoor air within airspace 2 in order to provide sufficient heating to provide a desired indoor air temperature of airspace 2.

The flow of hot gas refrigerant from the compressor through line 30B to intersection 34 is controlled by control 28, which includes a control valve capable of controlling the rate of flow of the hot gas refrigerant there through and thus through line 30B and into line 32 at intersection 34 and thus the flow rate of refrigerant moving toward and into mixing location 34 and mixture line 36. An upstream segment of line 30B extends from its branching intersection from line 30A to an inlet of control 28 while a downstream segment of line 30B extends from an outlet of control 28 to intersection 34. Control 28 controls the rate of flow of the refrigerant there through based on the temperatures sensed at temperature sensors 24 and 26, and typically based on the difference between the temperatures.

More particularly, temperature sensor 24 senses the temperature of the outside air prior to the heating of the air by heat exchanger 14 in duct 15 whereas temperature sensor 26 senses the temperature of the inside air within airspace 2 of building 4. These two temperature sensors 24 and 26 send a respective signal to control 28, which calculates the difference between the two temperatures and also calculates a desired flow rate of the hot gas refrigerant which should be used in order to provide a desired temperature of the refrigerant entering first heat exchanger 16 in order to further heat the air at heat exchanger 16 to the desired pre-entry temperature to provide the desired indoor temperature of the air within airspace 2 of building 4. Thus, control 28 controls the rate of flow of the refrigerant there through and thus the percentage of the amount of the hot gas refrigerant used to form the mixture of the hot gas refrigerant and hot liquid refrigerant at intersection 34 in response to the temperatures sensed by sensors 24 and 26, and more particularly in response to the difference therebetween.

It is noted that system 1 may also be modified somewhat in a manner that still provides for the mixing of the hot gaseous refrigerant discharged from compressor 12 and the hot liquid refrigerant discharged from first heat exchanger 14. For instance, compressor 12 may have two outlets so that a first compressor discharge line or hot gas line extends downstream from one of the outlets to a connection with the first heat exchanger 14 inlet and so that a second compressor discharge line or hot gas line extends downstream from the other of the outlets to a mixing location or intersection (similar to 34) with the first heat exchanger discharge line. In this case, a mixture line like line 36 would likewise extend downstream from the mixing location or intersection to the inlet of second heat exchanger 16. Control valve 28 would still be connected inline along the compressor discharge line leading to the intersection, thereby likewise controlling the downstream flow of hot gaseous refrigerant toward the intersection and the mixture line.

In either of the configurations for providing the mixture, the rejection of heat from the hot gas and liquid mixture to the air at heat exchanger 16 thus cools the refrigerant, whereby cooled liquid refrigerant is moved from the outlet of heat exchanger 16 through line 38 to expansion valve 18 via the inlet thereof, and subsequently through the outlet thereof through line 40 to heat exchanger 22. Heat is thus rejected from the underground heat source (soil/water) as discussed above to the refrigerant within heat exchanger 22 whereby heated liquid refrigerant exits heat exchanger 22 via discharge or release line 42 and enters compressor 12 via the inlet thereof to complete the circulation of the refrigerant through the circulation loop of the heat pump, whereby the recirculation of the refrigerant starts over again.

System 1 in one preferred embodiment thus provides a highly efficient thermal system utilizing an underground source heat pump and dedicated outside air unit to heat outside air for a building. The concept of mixing the hot gas from the compressor with hot liquid coming from the first heat exchanger in order provide heat to the second heat exchanger within the airflow duct significantly enhances this efficiency.

In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed.

Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described. 

1. A thermal system comprising: an airflow duct; a compressor; a first heat exchanger which is in the airflow duct and has a first heat exchanger inlet in fluid communication with the compressor and a first heat exchanger outlet; a second heat exchanger which is in the airflow duct and which has a second heat exchanger inlet and a second heat exchanger outlet; a compressor discharge line connected to and extending downstream from the compressor; a first heat exchanger discharge line connected to the first heat exchanger outlet; a mixture line which is connected to the second heat exchanger inlet and is in fluid communication with the compressor discharge line and first heat exchanger discharge line; and a refrigerant which is movable through the first heat exchanger, second heat exchanger, compressor, compressor discharge line, first heat exchanger discharge line, and mixture line.
 2. The system of claim 1 further comprising a flow rate control valve positioned to control a flow rate of the refrigerant toward the mixture line.
 3. The system of claim 2 further comprising an outside air temperature sensor; and an inside air temperature sensor; wherein the flow rate control is in communication with the temperature sensors and controls the flow rate based on inside and outside air temperatures sensed respectively by the inside and outside air temperature sensors.
 4. The system of claim 3 further comprising a building defining an enclosed airspace; an exit opening of the airflow duct in fluid communication with the enclosed airspace; and an entrance opening of the airflow duct in fluid communication with outside air external to the building; wherein the inside air temperature sensor is inside the enclosed airspace.
 5. The system of claim 1 further comprising an inlet of the compressor; a third heat exchanger having a third heat exchanger inlet and a third heat exchanger outlet; and a third heat exchanger discharge line connected to the third heat exchanger outlet and the inlet of the compressor.
 6. The system of claim 5 further comprising a second heat exchanger discharge line connected to the second heat exchanger outlet and the third heat exchanger inlet.
 7. The system of claim 6 further comprising an expansion valve having an expansion valve inlet and an expansion valve outlet; a first segment of the second heat exchanger discharge line connected to the outlet of the second heat exchanger and the expansion valve inlet; and a second segment of the second heat exchanger discharge line connected to the expansion valve outlet and the inlet of the third heat exchanger.
 8. The system of claim 5 wherein the third heat exchanger is a ground coupled heat exchanger.
 9. The system of claim 1 further comprising a building defining an enclosed airspace; an exit opening of the airflow duct in fluid communication with the enclosed airspace; an entrance opening of the airflow duct in fluid communication with outside air external to the building; an outside air temperature sensor outside the enclosed airspace; an inside air temperature sensor inside the enclosed airspace; a flow rate control valve which is in communication with the temperature sensors and controls a flow rate of the refrigerant toward the mixture line based on inside and outside air temperatures sensed respectively by the inside and outside air temperature sensors; an inlet of the compressor; a third heat exchanger having a third heat exchanger inlet and a third heat exchanger outlet; a second heat exchanger discharge line connected to the second heat exchanger outlet and the third heat exchanger inlet; and a third heat exchanger discharge line connected to the third heat exchanger outlet and the inlet of the compressor.
 10. The system of claim 9 further comprising an expansion valve having an expansion valve inlet and an expansion valve outlet; a first segment of the second heat exchanger discharge line connected to the second heat exchanger outlet and the expansion valve inlet; and a second segment of the second heat exchanger discharge line connected to the expansion valve outlet and the third heat exchanger inlet.
 11. A method comprising the steps of: providing first and second heat exchangers in an airflow duct; discharging heated refrigerant from a compressor; moving a first portion of the heated refrigerant discharged from the compressor into the first heat exchanger; releasing the first portion from the first heat exchanger; mixing a second portion of the heated refrigerant discharged from the compressor with the first portion released from the first heat exchanger to form a mixture; delivering the mixture to the second heat exchanger; and blowing air through the airflow duct to transfer heat from the first and second heat exchangers to the air.
 12. The method of claim 11 wherein the step of discharging comprises discharging heated refrigerant from the compressor into a compressor discharge line; the step of releasing comprises releasing the first portion from the first heat exchanger into a first heat exchanger release line; further comprising the step of moving the first and second portions respectively from the first heat exchanger release line and compressor discharge line into a mixture line; and wherein the step of delivering comprises moving the mixture through the mixture line to the second heat exchanger.
 13. The method of claim 11 further comprising the step of controlling with a flow rate control valve a rate of flow of the refrigerant toward a mixing location at which the first and second portions are mixed to form the mixture.
 14. The method of claim 13 further comprising the steps of sensing an outside air temperature outside a building; and sensing an inside air temperature of an enclosed airspace within the building; wherein the step of blowing comprises blowing outside air from outside the building through the airflow duct into the enclosed airspace; and the step of controlling comprises controlling the rate of flow based on the inside and outside air temperatures.
 15. The method of claim 11 further comprising the steps of discharging the refrigerant from the second heat exchanger to a third heat exchanger; and moving the refrigerant from the third heat exchanger to an inlet of the compressor.
 16. The method of claim 15 wherein the third heat exchanger is a ground coupled heat exchanger.
 17. The method of claim 15 wherein the step of discharging comprises moving the refrigerant from the second heat exchanger to an expansion valve and from the expansion valve to the third heat exchanger.
 18. The method of claim 11 further comprising the steps of sensing an outside air temperature outside a building; sensing an inside air temperature of an enclosed airspace within the building; based on the inside and outside air temperatures, controlling with a flow rate control valve a rate of flow of the refrigerant toward a mixing location at which the first and second portions are mixed to form the mixture; and moving the refrigerant from the second heat exchanger to an expansion valve, from the expansion valve to the third heat exchanger, and from the third heat exchanger to an inlet of the compressor; wherein the step of blowing comprises blowing outside air from outside the building through the airflow duct into the enclosed airspace.
 19. A method comprising the steps of: providing first and second heat exchangers in an airflow duct; moving a first portion of heated gaseous refrigerant into the first heat exchanger so that the refrigerant is cooled and discharged from the first heat exchanger as heated liquid refrigerant; mixing a second portion of the heated gaseous refrigerant with the discharged heated liquid refrigerant to form a mixture; delivering the mixture to the second heat exchanger; and blowing air through the airflow duct to transfer heat from the first and second heat exchangers to the air.
 20. The method of claim 19 further comprising the steps of sensing an outside air temperature outside a building; sensing an inside air temperature of an enclosed airspace within the building; based on the inside and outside air temperatures, controlling with a flow rate control valve a rate of flow of the refrigerant toward a mixing location at which the first and second portions are mixed to form the mixture; and moving the refrigerant from the second heat exchanger to an expansion valve, from the expansion valve to the third heat exchanger, and from the third heat exchanger to an inlet of the compressor; wherein the step of blowing comprises blowing outside air from outside the building through the airflow duct into the enclosed airspace. 